1. Field of the Invention
The present invention relates to an electrolytic capacitor.
2. Related Background Art
In general, a capacitor device employed in an electrolytic capacitor is made by using a metal (so-called valve metal) capable of forming an insulative oxidized film, such as aluminum, titanium, and tantalum, as an anode; forming an insulative oxidized film by anodizing the surface of the valve metal; then forming a solid electrolyte layer made of an organic compound or the like substantially functioning as a cathode; and further providing a conductive layer made of graphite, silver, or the like as a cathode.
Known as methods for achieving a low impedance in such an electrolytic capacitor are those lowering equivalent series inductance (ESL) and equivalent series resistance (ESR). An electrolytic capacitor omitting a lead frame for lowering ESR is disclosed in Japanese Patent Application Laid-Open No. 2001-102252. The electrolytic capacitor disclosed in this publication is one in which a two-terminal type capacitor device having a pair of electrodes is mounted on one face of a substrate, whereas an electrode on the device mounting surface of the substrate and an electrode on the backside are connected to each other via a through hole.
However, the following problem exists in the above-mentioned conventional electrolytic capacitor. Namely, since the distance between the anode electrode and cathode electrode formed on the device mounting surface is long, the distance between a pair of through holes extending along the thickness of the substrate from the anode and cathode electrodes is long. Therefore, the conventional electrolytic capacitor has been problematic in that the ESL caused by currents flowing through these through holes is so high that impedance is not lowered sufficiently.
For solving the above-mentioned problem, it is an object of the present invention to provide an electrolytic capacitor with a further lowered impedance.